Ill 



The Classification of Protozoa 



Taxonomy prior to 1900 Prospective sources of taxonomic data 



Taxonomic systems of the twentieth cen- The identification of Protozoa 

 ^"■^y Literature cited 



X 



HE CLASSIFICATION of Protozoa scrvcs various useful purposes 

 in addition to furnishing a system for filing species in appropriate cata- 

 logs. A sound taxonomy favors progress in comparative morphology and 

 physiology since it facilitates correlation of the information bearing on 

 related organisms. The projection of experimental and observational data 

 on a taxonomic background also is helpful in planning investigations to 

 extend or limit the application of preliminary findings. In fact, without 

 some knowledge of taxonomic relationships, the choice of material for 

 certain types of research would be analogous to "wildcat" drilling for oil. 

 Although a certain amount of "wildcatting" is always needed, the orderly 

 development of a field often depends extensively upon systematically 

 directed efforts. As more is learned about the interrelationships of Pro- 

 tozoa, the benefits derived from the field of taxonomy will become increas- 

 ingly important. 



A major aim of taxonomy^ is the assignment of organisms to species 

 and larger groups on the basis of degree of kinship. If the available data 

 are extensive enough and have been interpreted correctly, such a tax- 

 onomic system not only indicates degrees of relationship among existing 

 species, but also furnishes sound clues to phylogenetic relationships. Un- 

 fortunately, this taxonomic ideal has not yet been realized for the Phylum 

 Protozoa as a whole. 



The limitations of current systems are numerous. In the first place, 

 the boundaries of the phylum are subject to debate, particularly in the 

 case of phytoflagellates. In studying the Phytomastigophorea and their 



^ General problems of zoological classification and conventional taxonomic procedures 

 have been reviewed in a compact monograph by Caiman (6). 



103 



